The present invention relates to disposable diapers and more particularly to a stretchable waistband for a disposable diaper.
Diapers of the disposable type have, during recent years, come into widespread use. Their increased popularity can be attributed to their elimination of the inconvenience of having to wash diapers, their ease of use, particularly when removing a soiled diaper from an infant, and the dryer comfort they provide due to the use of improved materials relative to conventional reusable diapers.
While the use of disposable diapers has greatly increased due to their various advantages over reusable diapers, they continue to have several defects necessitating continued work toward their improvement. One of these defects is urine leakage in the waist area of the diaper. A wide variety of diaper elastic waist constructions have been developed in attempts to remedy the problem. However none of these have been satisfactory to the point of enjoying any significant commercial success. Typical drawbacks are complexity of the construction or adding of excessive components which make the diaper difficult to manufacture and add unacceptable material costs, a construction which is inherently difficult to manufacture, lack of durability of the construction, insufficient elasticity either entirely or in the area of the waist where it is most needed, and lack of aesthetic appeal. For example, an elastic waist construction is disclosed in Schaar U.S. Pat. No. 3,995,640 in which an elastic strip or strips or an elastic loop is placed transversely in the waist area of the diaper. In the case of elasticization using the strip, the folding of the diaper waist end, which must take place after the continuous web is cut into individual diapers, is extremely difficult to accomplish. This is because the leg elastic will retract the individual diaper lengthwise if it is not held entirely flat while moving rapidly along the production line until packaging and the folding operation while simultaneously holding the diaper flat cannot be done readily. This problem is also true of the elastic loops and, moreover, the arranging of the loops is far too intricate to permit their attachment to diapers during high speed production.
In Kozak U.S. Pat. No. 4,036,233, an example of an elastic waist construction is disclosed in which the necessary elasticity is actually lacking. A topsheet and backsheet are provided and one of the two sheets comprises a material which is stretchable relative to the other sheet. The two sheets are bonded together in the waistband area. Since the stretchable sheet is intended to provide stretch to the waist area, the nonstretchable sheet is provided with slits or openings so that it does not prevent movement of the stretchable sheet. The two sheets, however, remain bonded together along the edge of the waist and the slits do not extend to any significant degree beyond the area of stretching tension applied to the waist. Thus, in fact, almost all waist tension will be nevertheless carried by the nonstretchable material and very little waist stretch will occur.
In Jacob U.S. Pat. No. 3,800,796, an elasticized waist is provided by means of a fastening tape incorporating a stretchable mid-portion. The problem with this construction is that the flexibility of the tape permits excessive pivoting movement of the diaper side waist portions during movement by the wearer. The result is skewing of the side waist portions and deterioration of the waist fit to cause increased urine leakage problems.